1. Field of the Invention
The present invention relates to catalytic surfaces, and, more specifically, to catalytic surfaces for active protection from air or water borne toxins by passivation and adsorption of toxic materials.
2. Description of the Prior Art
There is an urgent need for the development of effective means to protect people and the environment from the exposures of toxic chemicals and other threat agents irrespective of the cause of exposure, accidental or due to terrorist act. Moreover, there is a need to protect against prolonged exposure to small amounts of toxic chemicals (such as pesticides), since persistent encounters with small quantities of toxic chemicals, especially in a closed environment, may be more dangerous than a one-time encounter with a larger quantity. The existing technologies use barrier protection to protect people and the environment involving materials of high absorbing capacity. The most widely used adsorbent is active charcoal, which leads to the development of bulky materials. Materials used in barrier protection are bulky and have only one useful life cycle. While the barrier technologies provide adequate protection, they have the serious technical problem of disposal of the materials at the end of their active life cycle because of the presence of toxic materials in concentrated form. Other concerns include weight, capacity and inconvenience during practical use.
Another existing technology regarding toxic chemicals is the use of enzymes. Enzymes are the most effective catalyst against chemical agents but have limited long-term stability. Also, they lose their catalytic activity during immobilization steps. See G. F. Drevon, K. Danielmeier, W. Federspiel, D. B. Stolz, D. A. Wicks, P. C. Yu & A. J. Russell, “High-activity enzyme-polyurethane coatings,” BIOTECHNOLOGY AND BIOENGINEERING, 79 (7): 785–794, 2002 and G. F. Drevon & A. J. Russell, “Irreversible immobilization of diisopropylfluorophosphtase in polyurethane polymers, BIOMACROMOLECULES, 1 (4): 571–576 (2000), both of which are incorporated herein by reference. Lack of stability and loss of catalytic activity render enzymes unsuitable for protection applications. Several techniques have been reported for stabilizing the enzymes—most of them focusing on their immobilization to a suitable substrate. However, chemical linking to the surface causes the enzymes to lose their activity substantially. Non-covalent immobilization of enzymes on vesicles provides an effective means to retain enzyme activity. See U.S. Pat. No. 5,663,387 to Singh, incorporated herein by reference. Deposition of a single layer of enzymes on a surface is good for a sensor application, but not adequate for chemical agent passivation applications, which require a larger amount of enzymes to effectively hydrolyze the toxic chemicals.